1. Field of the Invention
The present invention relates to a compound based on cyanine scaffold for diagnosing sepsis by selectively detecting glutathione.
2. Description of the Related Art
The amino acids containing thiol group (R—SH) are the components forming numbers of peptides playing an important role in maintaining oxidation-reduction homeostasis with keeping balance between the reduced free thiol and oxidized disulfide (non-patent reference 1).
Non-patent reference 2 describes that the abnormal levels of the amino acids containing thiol group (R—SH) are closely related to the development of liver injury, cancer, AIDS, osteoporosis, Alzheimer's disease, inflammatory bowel disease, and cardiovascular disease, etc. That is, if we measure and judge the level of biothiol, the amino acid that contains thiol group (R—SH), we can make early diagnosis for the related diseases.
Thus, a variety of fluorescent probes have been developed to detect selectively the amino acid containing thiol group (R—SH) among various amino acids in vivo. Particularly, according to non-patent reference 3, a probe is described in relation to the unique nucleophilic addition and substitution of thiol group. However, this probe does not select a specific amino acid containing thiol group (R—SH) each and selectively but select all the biothiols that contain R—SH such as cysteine, homocysteine, and glutathione, which draws a limitation in selective detection of each target amino acid.
Among these biothiols, glutathione is involved in cell functions, for example, intracellular redox activity, xenobiotic metabolism, intracellular signaling, and gene regulation, and also plays an important role in protecting cell damage caused by free radicals and reactive oxygen species. More precisely, glutathione is reacted to oxides in vivo, resulting in reversible glutathione disulfide (GSSG) that is the oxidized form of glutathione wherein two glutathione molecules are connected each other by disulfide bond (—S—S). By this reaction, in vivo oxidation-reduction potential is regulated.
To detect the said glutathione selectively, a few fluorescent probes based on organic dyes have been developed. For example, non-patent reference 4 describes the promising probe based on bis-spiropyran structure. Non-patent reference 5 describes the probe based on resorufin structure to detect selectively glutathione in blood plasma. Non-patent reference 6 describes the fluorescent sensor based on BODIPY structure to detect selectively glutathione in living cells.
Considering glutathione is a major intracellular antioxidant that exists in cell at the concentration of approximately 0.5˜10 mM, the detection of in vivo glutathione by using a near infrared ray (700˜900 nm) fluorescent probe is advantageous because it causes less biological damage and makes deeper penetration in tissue in the said wave-length range. However, those probes developed to detect glutathione using near infrared ray demonstrated not as excellent selectivity.
In the course of study to develop a probe usable for the selective detection of in vivo glutathione, the present inventors confirmed that the compound based on cyanine scaffold identified by the inventors could keep its structure even in intracellular environment and selectively react to glutathione among many amino acids containing thiol group (R—SH), exemplified by cysteine, homocysteine, and glutathione, etc, and displayed glutathione specific absorption spectrum or fluorescence spectrum, so that it could be efficiently used not only for the detection of glutathione in biosamples but also for the diagnosis of sepsis that can change the level of in vivo glutathione, leading to the completion of this invention.